Conventionally, international standard video encoding systems such as MPEG and ITU-TH.26× are adopted mainly on condition that a standardized input signal format called a “4:2:0” format is used. The 4:2:0 format represents a format for transforming a color moving image signal such as RGB into a luminance component (Y) and two color difference components (Cb and Cr) and reducing the number of samples of the color difference components to a half both in horizontal and vertical directions with respect to the number of samples of the luminance component. Since visibility of degradation for the color difference components is low compared with that for the luminance component, the conventional international standard video encoding system is adopted on condition that an amount of information on an object of encoding is reduced by performing down-sampling of the color difference components as described above before encoding is performed. On the other hand, according to the increase in resolution and the increase in gradation of a video display in recent years, a system for encoding an image with samples identical with the luminance components without down-sampling the color difference components is examined. A format in which the number of samples of the luminance components and the number of samples of the color difference components are identical is called a 4:4:4 format. In MPEG-4 AVC (ISO/IEC 14496-10)/ITU-T_H.264 standard (hereinafter referred to as AVC), for an encoding system for inputting the 4:4:4: format, a “high 444 profile” is decided. While the conventional 4:2:0 format is adopted on condition that the color difference components are down-sampled and is limited to color space definitions of Y, Cb, and Cr, there is no distinction of a sample ratio among color components in the 4:4:4 format, so it is possible to directly use R, G, and B other than Y, Cb, and Cr and use other multiple color space definitions. In the video encoding system in which the 4:2:0 format is used, since the color spaces are fixed as Y, Cb, and Cr, it is unnecessary to take into account types of color spaces during encoding processing. However, the AVC high 4:4:4: profile is a system in which the color space definition affects encoding processing itself. On the other hand, in the present high 4:4:4 profile, compatibility with other profiles for encoding the 4:2:0 format defined by the Y, Cb, and Cr spaces is taken into account. Thus, it cannot be said that the present high 4:4:4 profile is designed to optimize compression efficiency thereof.    Non-patent Document 1: MPEG-4 AVC (ISO/IEC 14496-10)/ITU-TH.264 standard